Life Itself: Its Origin and Nature
Ten years ago, Carl Sagan of Cornell University invited me to go with him to a conference held at a mountain-top astronomical observatory, high above the Armenian city of Yerevan. The conference, sponsored jointly by the US and USSR Academies of Science, had “Communication with Extraterrestrial Intelligence,” or CETI, as its topic. I recall it here since it is directly relevant to the new book by Francis Crick. Certainly it was the most fantastic of the many international scholarly gatherings I have attended. The agenda of the CETI Conference was twofold: to assess the chances that there are any extraterrestrial intelligent (ETI) beings with whom we might communicate (or who might be trying to communicate with us), and to decide on the most practical means by which we (or they) might effect such communication. An interdisciplinary group of about fifty scholars had been invited, mostly from the US and the USSR, to address these two questions.
On the very first day of the meeting it turned out that most of the participants were veteran CETI enthusiasts, who had come to Armenia convinced that there were many ETIs out in space and that radio was the way to get in touch with them. Accordingly, the real purpose of the conference seemed to be the formulation of an effective plea to the US and USSR governments to devote substantial funds to building giant radiotelescopes for CETI—one plan put forward at the meeting, for instance, called for the construction of 1,000 interlinked dish antennas, each 100 meters in diameter, at a cost of $10 billion (1971). The official proceedings of the CETI Conference were eventually published as a book
The first part of the conference was devoted to estimating the number, N, of potential ETI conversation partners in our galaxy, by means of the “Drake Formula,” devised by Sagan’s fellow Cornell astronomer Frank Drake. The Drake Formula states that:
N=R*fp*f e*fl*fi* fc*ft,
where R is the number of stars in our galaxy, fp the fraction of such stars that have planets, fe the fraction of such planets that are ecologically suitable for life, fl the fraction of ecologically suitable planets on which life actually has arisen, fi the fraction of planets on which, following the origin of life, intelligent beings have arisen, fc the fraction of planets with intelligent beings on which technologically competent civilizations arose capable of communicating with us, and, finally, ft the fraction of such civilizations that still exist at present and still might want to communicate with us.
Since R, the number of stars in our galaxy, is about a hundred billion, the Drake Formula indicates that, as long as none of the f fractions is vanishingly small, there should be many potential ETIs for …